1. Field of the Invention
The present invention relates to a dielectric composition, and to a dielectric film element employing the dielectric composition. More particularly, the present invention relates to a dielectric composition which is suitable for use in an electron emitter as an electron beam source in various devices and apparatus that utilize electron beams, such as displays (e.g., field emission displays (FEDs)), electron beam irradiation apparatus, light sources, electronic-component-manufacturing apparatus, and electronic circuit components; and to a dielectric film element employing the dielectric composition.
2. Description of the Related Art
As is generally known, the aforementioned electron emitter is configured such that a predetermined electric field is applied to an emitter section (electron emission section) in a vacuum having a predetermined vacuum level, whereby electrons are emitted from the emitter section. In application to FEDs, a plurality of electron emitters are two-dimensionally arrayed, and a plurality of phosphors corresponding to the electron emitters are arrayed with a predetermined spacing held therebetween. Among the two-dimensionally arrayed electron emitters, certain electron emitters are selectively driven so as to emit electrons therefrom. The emitted electrons collide with phosphors corresponding to the driven electron emitters. The phosphors hit by the electrons fluoresce, thereby displaying a desired image.
Specific examples of the electron emitter are disclosed in, for example, Japanese Patent Application Laid-Open (kokai) Nos. 01-311533, 07-147131, and 2000-285801 and Japanese Patent Publication (kokoku) Nos. 46-20944 and 44-26125. Such a disclosed electron emitter includes an emitter section formed of a fine conductive electrode having a pointed tip end portion, and a counter electrode provided so as to face the emitter section, and the electron emitter is configured such that when a predetermined drive voltage is applied to the emitter section and the counter electrode, electrons are emitted from the tip end portion of the emitter section.
Accordingly, forming such a fine conductive electrode having a tip end portion requires micromachining that employs etching, forming, or the like, and thus production of the electron emitter involves a complicated process. Meanwhile, a certain high level of drive voltage must be applied to the electron emitter for emitting a predetermined number of electrons from the tip end portion of the conductive electrode to a vacuum having a predetermined vacuum level. Therefore, driving the electron emitter requires an expensive drive element (e.g., IC) which is applicable to high-voltage drive.
Thus, the above-disclosed electron emitter, which includes an emitter section formed of a conductive electrode, involves a problem in that high cost is required for producing the electron emitter per se, or a device employing the electron emitter.
Therefore, an electron emitter in which an emitter section is formed of a dielectric material is devised, which emitter is disclosed in, for example, Japanese Patent Application Laid-Open (kokai) Nos. 2004-146365 and 2004-172087. General findings regarding electron emission in the case where a dielectric material is used to form an emitter section are disclosed in, for example, Yasuoka and Ishii, “Pulsed Electron Source Using Ferroelectric Cathode electrode,” Applied Physics, Vol. 68, No. 5, pp. 546-550 (1999); V. F. Puchkarev and G. A. Mesyats, “On the Mechanism of Emission from the Ferroelectric Ceramic Cathode electrode,” J. Appi. Phys., Vol. 78, No. 9, 1 Nov., 1995, pp. 5633-5637; and H. Riege, “Electron Emission Ferroelectrics—a Review,” Nucl. Instr. and Meth. A340, pp. 80-89 (1994).
The electron emitters disclosed in Japanese Patent Application Laid-Open (kokai) Nos. 2004-146365 or 2004-172087 (hereinafter called merely “conventional electron emitters”) are configured such that a cathode electrode covers a portion of the top surface of an emitter section formed of a dielectric material, and an anode electrode is provided on the bottom surface of the emitter section, or on the top surface of the emitter section with a predetermined spacing maintained between the same and the cathode electrode. Specifically, the electron emitters are configured such that an exposed portion of the top surface of the emitter section at which neither the cathode electrode nor the anode electrode is formed is present in the vicinity of a peripheral edge portion of the cathode electrode.
The conventional electron emitter is operated as follows. In a first stage, voltage is applied between the cathode electrode and the anode electrode such that the cathode electrode is higher in electric potential. An electric field induced by the applied voltage brings the emitter section (in particular, the aforementioned exposed portion) into a predetermined polarization state. In a second stage, voltage is applied between the cathode electrode and the anode electrode such that the cathode electrode is lower in electric potential. At this time, primary electrons are emitted from the peripheral edge portion of the cathode electrode, and the polarization of the emitter section is inverted. The primary electrons collide with the exposed portion of the polarization-inverted emitter section, whereby secondary electrons are emitted from the emitter section (particularly from the exposed portion). The secondary electrons fly in a predetermined direction by means of an externally applied, predetermined electric field; i.e., the electron emitter emits electrons.